The present invention concerns an injection valve for a vacuum wax injection installation.
The vacuum wax injection process involves the production of a wax mold by filling a suitable hollow rubber mold with wax which then hardens in the rubber mold. In order to prevent the formation of air bubbles in the mold, the hollow rubber mold is evacuated prior to the injection of the wax into the mold, by the application of a reduced pressure to the rubber mold.
When carrying out that process in a vacuum wax injection installation therefore, the installation includes an injection valve which serves to communicate a mold into which wax is to be injected firstly with a chamber providing a vacuum and then with a chamber containing liquid wax. The valve must have a valve-closed position, an evacuation position for evacuation of the mold, and a wax injection position. The valve, from the structural point of view, further has a connecting element against which the hollow rubber mold can be sealingly pressed for the evacuation and the wax-injection phases.
Hitherto such injection valves for vacuum wax injection installations have been of an extremely complicated configuration, usually comprising various electronic, mechanical or similar components for producing the operating procedure involved (evacuation of the mold, interruption of the applied vacuum and injection of the wax). Injection valves of this kind, but of a simpler design configuration, tended to be highly complicated to operate as, at the same time as the hollow rubber mold being pressed against the connecting element, the various operating phases involved had to be successively triggered off by way of a control member such as a lever.